Modulating the Coordinatively Unsaturated Mo Species through Oxide–Support Interaction for Enhanced Reverse Water–Gas Shift Activity

The coordinatively unsaturated metal species of metal oxides always play important roles in both constructing oxide-based catalysts and catalyzing some reactions. However, it is a challenge to tune its surface density and stability due to the uncontrolled reduction. Herein, we deposit MoO₃ onto different oxides via the simple dry combustion method and find that the host oxides affect formation of coordinatively unsaturated Mo species through the oxide-support interaction, thus strongly altering their reverse water-gas shift activity. The strong oxide-support interaction lowers the reduction temperature of the amorphous oligomeric MoO_<i>x</i> species on m-ZrO₂ and a-TiO₂ supports, generating high surface content of coordinatively unsaturated MoO_2-<i>x</i> species with high stability, compared with those on CeO₂, γ-Al₂O₃, and SiO₂ supports. Consequently, MoO₃/m-ZrO₂ displays the highest CO₂ reaction rate through the formate reaction pathway, i.e., 19.2 mmol_CO2·g_catal^-1·h^-1, followed by MoO₃/a-TiO₂ (12.8 mmol_CO2·g_catal^-1·h^-1), which are 21 and 14 times higher than that of MoO₃, respectively. Moreover, the MoO₃/m-ZrO₂ and MoO₃/a-TiO₂ catalysts also display good stability during the 60 h reaction due to the strong interface bonding. This work provides a way to mediate catalytic performance of metal oxide catalysts through the oxide-support interaction.